Hydraulic system for a motor vehicle having a hinged convertible top

ABSTRACT

A hydraulic system for a motor vehicle having a convertible top ( 2 ) which can be folded back has a convertible-top control system ( 1 ) and further hydraulic control devices ( 3, 4 ) which can be activated by a common hydraulic pump ( 6 ). In hydraulic lines ( 8, 9 ) leading to the convertible-top control system ( 1 ) there are arranged hydraulic valves ( 13, 14 ) which enable optional operation of the convertible-top control system ( 1 ) or of the further control devices ( 3, 4 ). Because of this, the hydraulic system turns out to be particularly simple structurally.

FIELD AND BACKGROUND OF THE INVENTION

The invention relates to a hydraulic system for a motor vehicle having aconvertible top which can be folded back, with a convertible-top controlsystem which can be operated by a hydraulic pump.

Hydraulic systems of this type are frequently used in modern motorvehicles described as convertibles and are known from practicalexperience. For safety reasons the convertible top can only be opened orclosed when the motor vehicle is at a standstill or when traveling at alow speed, for example of less than 10 km/h. The other control deviceswhich are arranged in the motor vehicle serve, for example, for theactivation of adjustable spring struts, a transmission control system oran additional steering system for a rear axle. In known motor vehiclesthese hydraulic control devices are activated via their own hydrauliccircuits and via hydraulic pumps or pressure accumulators additionallyarranged in the motor vehicle.

SUMMARY OF THE INVENTION

The invention is based on the problem of providing a hydraulic system ofthe type mentioned at the beginning in such a manner that it isconstructed as simply as possible and can be produced cost-effectively.

According to the invention, this problem is solved in that in ahydraulic line, which leads to the convertible-top control system, thereis arranged a controllable hydraulic valve for the activation of afurther hydraulic control device for operating a further functional unitof the motor vehicle.

In one refinement the convertible-top control system and the furtherhydraulic control device are switched on at the same time, there being aclear distinction between the power consumption of the convertible-topcontrol system and the control device as an alternative to this, thefurther hydraulic control device can be activated only with theconvertible-top control system switched off.

This enables the hydraulic system according to the invention to be usedfor the activation of the further hydraulic control devices when theconvertible-top control system is not in use. Since the two devices haveapproximately the same power requirement, the hydraulic pump does notneed to be adapted for the system according to the invention. Because ofthis, the hydraulic system according to the invention is of particularlysimple construction and can be produced cost-effectively. Since, thanksto the invention, in each case either the convertible-top control systemor one of the further hydraulic devices can be activated, pressurefluctuations do not arise in the hydraulic lines. Therefore, only asmall pressure accumulator or none at all is needed as a buffer foroperation of the further control devices. This results in a furtherreduction in the structural design of the system according to theinvention.

The system according to the invention requires a particularly smallstructural design if a control electronics unit of the hydraulic pump isprovided for the activation of the hydraulic valve. Furthermore, adesignated pressure level can be produced for each of the hydrauliccontrol devices by the simultaneous activation of the hydraulic pump andof the hydraulic valve.

According to another advantageous development of the invention, mutualinterference of two further control devices can be avoided if thehydraulic pump is designed for the conveying of hydraulic oil in bothdirections, and a hydraulic valve is arranged in each of the hydrauliclines leading to the convertible-top control system.

According to another advantageous development of the invention, amultiplicity of hydraulic control devices can be operated in a simplemanner with particularly low outlay if a plurality of branches to thehydraulic control devices are arranged in one of the hydraulic linesleading to the convertible-top control system. If certain hydrauliccontrol devices are only to be activated separately, this can beachieved via further hydraulic valves which can be controlled by thecontrol electronics unit.

In the case of hydraulic control devices which can be activated inparallel, a drop in pressure in one of the hydraulic control deviceswhen a further hydraulic device is switched on can be avoided in asimple manner if a nonreturn valve is in each case arranged between thebranches and the control devices. Because of the nonreturn valves,discharging of the hydraulic oil from the hydraulic control deviceactivated first is reliably avoided.

According to another advantageous development of the invention, aplurality of hydraulic control devices, which require the same volumeflow of hydraulic oil at essentially the same time, can be operated witha small number of hydraulic lines if one hydraulic line is designed as areturn line of one of the hydraulic control devices and as a supply lineof a further hydraulic control device.

According to another advantageous development of the invention, amultiplicity of hydraulic control devices can be operated without mutualinterference if a plurality of hydraulic valves, which in each caseactivate hydraulic control devices, are arranged in series in one of thehydraulic lines, each of the hydraulic valves being formed as a shuttlevalve. By means of this design, when one hydraulic control devicearranged close to the hydraulic pump is activated, all of the hydrauliccontrol devices arranged further away are automatically switched off.Each of the hydraulic control devices is hereby assigned a priority. Theconvertible-top control system can therefore be arranged next to thehydraulic pump and, for example, the hydraulic control device for therear-wheel steering system can be arranged in second place.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention permits numerous embodiments. To further clarify its basicprinciple a plurality of these are represented in the drawings and aredescribed in the following. The drawings show in

FIG. 1 a schematic representation of a hydraulic system according to theinvention with a convertible-top control system and two control devices,and

FIGS. 2-5 further embodiments of the hydraulic system according to theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a hydraulic system according to the invention with aconvertible-top control system 1 for opening and closing a convertibletop 2 of a motor vehicle, and with two further hydraulic control devices3, 4. The hydraulic system has a hydraulic pump 6, which can be drivenin both directions by an electric motor 5, and a control electronicsunit 7. With the control electronics unit 7, the conveying direction andthe conveying volume of the hydraulic pump 6 can be controlled. Twohydraulic lines 5, 9 lead from the hydraulic pump 6 to theconvertible-top control system 1. The convertible-top control system 1has a hydraulic cylinder 10 which is coupled to the convertible top 2 ofthe motor vehicle. To simplify the drawing, a single hydraulic cylinder10 is shown. Arranged in the hydraulic lines 8, 9 are hydraulic valves11, 12 which can in each case be controlled electrically by the controlelectronics unit 7 and with which the hydraulic control devices 3, 4 canbe activated. Furthermore, FIG. 1 shows that pressure control valves 13,14, which are connected to a common reservoir 15, are arranged in thehydraulic lines 8, 9. Return lines 16-18 lead in each case from theconvertible-top control system 1 and the hydraulic control devices 3, 4into the reservoir 15.

The hydraulic valves 11, 12 are designed as shuttle valves and in thebasic position shown are preloaded into a position which enables theconvertible top 2 to be activated. Since the hydraulic control devices3, 4 are in each case connected to one of the hydraulic lines 8, 9, ineach case only one of the hydraulic control devices 3, 4 can beactivated, corresponding to the conveying direction of the hydraulicpump 6. Electric signal lines 19 lead from the control electronics unit7 to switches and measuring devices which are not shown. The measuringdevices may, for example, be a motor-vehicle speedometer. It is therebypossible, for example above a designated motor-vehicle speed, to blockthe convertible-top control system 1 by the control electronics unit 7.

The hydraulic control devices 3, 4 may, for example, be a leveladjustment of spring struts of the motor vehicle. By this means, withthe system according to the invention compensation for the spring travelor a difference in wheel load when loading, or the raising and loweringof the motor vehicle, for example as a function of the speed thereof,may be undertaken.

FIG. 2 shows a further embodiment of the hydraulic system according tothe invention with a convertible-top control system 1 and with ahydraulic control device 2 for a rear-wheel steering system of the motorvehicle. The system according to the invention has a hydraulic pump 22which draws in hydraulic oil from a reservoir 23 and conveys it via ahydraulic line 24 to a controllable hydraulic valve 25. The hydraulicvalve 25 has two switching positions for the optional activation of theconvertible-top control system( 20 and op the control device 21 for therear-wheel steering system. Nonreturn valves 26, 27 are in each casearranged between the hydraulic valve 25 and the convertible-top controlsystem 20 and also the control device 21 for the rear-wheel steeringsystem. The nonreturn valves 26, 27 prevent hydraulic oil from flowingback via the hydraulic pump 22 into the reservoir 23. The hydrauliccontrol device 21 of the rear-wheel steering system has a double actiondifferential cylinder 28 which can be activated via two electricallycontrollable valves 29, 30. The convertible-top control system 20 hastwo hydraulic cylinders 31, 32 which can in each case be activated bymeans of controllable valves 33, 34 and nonreturn valves 35, 36.Furthermore, FIG. 2 shows that the convertible-top control system 20 andthe control device 21 for the rear-wheel steering system are in eachcase connected to the reservoir 23 via return line 37, 38.

FIG. 3 shows a further embodiment of the hydraulic system according tothe invention with a convertible-top control system 39 and two furthercontrol devices 40, 41. The convertible-top control system 39 isconnected via a hydraulic line 42 to a hydraulic pump 44 conveyinghydraulic oil from a reservoir 43. A plurality of branches 45, 46 forthe control device s 40, 41 are arranged in the hydraulic line 42.Hydraulic valves 48, 49, which can be activated by a common controlelectronics unit 47, and in each case one nonreturn valve 50, 51 arearranged between the control devices 40, 41 and t he branches 45, 46.The convertible-top control system 39 likewise has a nonreturn valve 52and an activatable hydraulic valve 53. The control electronics unit 47serves to switch the hydraulic valves 48, 49, 53 in such a manner thatthe convertible-top control system 39 and the two control devices 40, 41can be operated at the same time. The control devices 40, 41 may, forexample, be an adjustable differential of the driving axle of the motorvehicle or a hydraulic boost for a manually-operated transmission (notshown). Furthermore, the control devices 40, 41 can be designed for thehydraulic boosting of a motor-vehicle clutch (not shown). Such controldevices 40, 41 require a low volume flow of hydraulic oil, so that thereis no risk of mutual interference between the two control devices 40, 41when they are operated at the same time.

FIG. 4 shows a further embodiment of the hydraulic system according tothe invention, with a convertible top control system 54 and two furthercontrol devices 55, 56. The system according to the invention has ahydraulic pump 57 and a plurality of hydraulic valves 59-61 arranged inseries in a hydraulic line 58. The hydraulic valves 59-61 are in eachcase designed as a shuttle (changeover) valve having two switchingpositions, so that either the control device 55, 5 and theconvertible-top control system 54, which are connected to the respectivehydraulic valve 59-61, or the following hydraulic valve 59-61 isconnected to the hydraulic pump 57. As a result, by correspondingswitching of the hydraulic valves 59, 61 in each case only theconvertible-top control system 54 or only one of the control devices 55,56 can be operated.

The control devices 55, 56 may, for example, be designed for adjustingaerodynamic components of the motor vehicle as a function of themotor-vehicle speed, or for adjusting a radiator or air-flow aperturesfor the motor-vehicle radiator as a function of the cooling-airrequirements. The control devices 55, 56 may furthermore serve foradjusting vehicle seats or for locking vehicle doors or for activating aparking brake.

FIG. 5 shows a further embodiment of the hydraulic system according tothe invention, with a convertible-top control system 62 and a hydrauliccontrol device 63. A hydraulic line 64 is designed in this case as areturn line of the convertible-top control system 62 and at the sametime as a supply line of the control device 63. Furthermore, thehydraulic system has two hydraulic valves 65, 66 by means of which thecontrol device 63 and the convertible-top control system 62 can in eachcase be activated or bypassed.

The control device 63 is, for example, a control device for headrestraints, which control device only builds up a slight difference inpressure.

We claim:
 1. A hydraulic system for a motor vehicle having a convertibletop which is able to be folded back, with a convertible-top controlsystem which is able to be operated by a hydraulic pump, wherein in ahydraulic line (8, 9, 24, 42, 58, 64), which leads to theconvertible-top control system (1, 20, 39, 54, 62), there is arranged acontrollable hydraulic valve (11, 12, 25, 48, 49, 53) for activation ofa hydraulic control device (3, 4, 21, 40, 41, 55, 56, 63) for operatinga further functional unit of the motor vehicle, wherein the hydraulicpump is provided for conveying of hydraulic oil in both directions, andsaid hydraulic valve (11, 12) is arranged respectively in each of thehydraulic lines (8, 9) leading to the convertible-top control system(1).
 2. The hydraulic system as claimed in claim 1, wherein saidconvertible-top control system (1, 20, 39, 54, 62) and said furtherhydraulic control device (3, 4, 21, 40, 41, 55, 56, 63) are switched onat the same time.
 3. The hydraulic system as claimed in claim 1, whereinsaid further hydraulic control device (3, 4, 21, 40, 41, 55, 56, 63) isactivatable with the convertible-top control system switched off.
 4. Thehydraulic system as claimed in claim 1, wherein a control electronicsunit (7, 47) of the hydraulic pump (6, 44) is provided for activation ofthe hydraulic valve (11, 12, 48, 49, 53).
 5. The hydraulic system asclaimed in claim 1, wherein a plurality of branches (45, 46) to thehydraulic control devices (40, 41) are arranged in one of the hydrauliclines (42) leading to the convertible-top control system (39).
 6. Thehydraulic system as claimed in claim 5, wherein a nonreturn valve (50,51) is in each case arranged between the branches (45) and the hydrauliccontrol devices (40, 41).
 7. The hydraulic system as claimed in claim 1,wherein a plurality of hydraulic valves (59-61), which in each caseactivate hydraulic control devices (convertible-top control system 54,55, 56), are arranged in series in said hydraulic line (58), each of thehydraulic valves (59-61) being a changeover valve.
 8. A hydraulic systemfor a motor vehicle having a convertible top which is able to be foldedback, with a convertible-top control system which is able to be operatedby a hydraulic pump, wherein in a hydraulic line (8, 9, 24, 42, 58, 64),which leads to the convertible-top control system (1, 20, 39, 54, 62),there is arranged a controllable hydraulic valve (11, 12, 25, 48, 49,53) for activation of a further hydraulic control device (3, 4, 21, 40,41, 55, 56, 63) for operating a further functional unit of the motorvehicle, wherein said hydraulic line (64) is a return line of theconvertible-top control system and as a supply line of a furtherhydraulic control device.
 9. The hydraulic system as claimed in claim 8,wherein the hydraulic pump is provided for conveying of hydraulic oil inboth directions, and said hydraulic valve (11, 12) is arrangedrespectively in each of the hydraulic lines (8, 9) leading to theconvertible-top control system (1).
 10. The hydraulic system as claimedin claim 8, wherein said convertible-top control system (1, 20, 39, 54,62) and said further hydraulic control device (3, 4, 21, 40, 41, 55, 56,63) are switched on at the same time.
 11. The hydraulic system asclaimed in claim 8, wherein said further hydraulic control device (3, 4,21, 40, 41, 55, 56, 63) is activatable with the convertible-top controlsystem switched off.
 12. The hydraulic system as claimed in claim 8,wherein a control electronics unit (7, 47) of the hydraulic pump (6, 44)is provided for activation of the hydraulic valve (11, 12, 48, 49, 53).13. The hydraulic system as claimed in claim 8, wherein a plurality ofbranches (45, 46) to the hydraulic control devices (40, 41) are arrangedin the hydraulic lines (42) leading to the convertible-top controlsystem (39).
 14. The hydraulic system as claimed in claim 13, wherein anonreturn valve (50, 51) is in each case arranged between the branches(45) and the hydraulic control devices (40, 41).
 15. The hydraulicsystem as claimed in claim 8, wherein a plurality of hydraulic valves(59-61), which in each case activate hydraulic control devices(convertible-top control system 54, 55, 56), are arranged in series insaid hydraulic line (58), each of the hydraulic valves (59-61) being achangeover valve.